Micro-fluid ejection head such as used in ink jet printers are a key component of ink jet printer devices. The processes used to construct such micro-fluid ejection heads require precise and accurate techniques and measurements on a minute scale. Some steps in the ejection head construction process are necessary but can be damaging to the ejection head. Such damage to the ejection head affects the quality of fluid output, and, therefore, has an affect on the value of the ejection device containing the ejection head.
One example of a technique that can result in such damage to an ejection head is the removal of an etch mask layer from photoresist planarization and protection layer on a semiconductor chip in a given ejection head. Ejection heads include a silicon substrate and a plurality of layers including passivation layers, conductive metal layers, resistive layers, insulative layers, and protective layers on the substrate. Fluid feed holes or fluid supply slots are formed in the substrate and various layers in order for fluid to be transferred through the holes or slots to ejection devices on a substrate surface. Such holes of slots are often formed through the semiconductor chip using deep reactive ion etching (DRIE) or mechanical techniques such as grit blasting. A planarization and protection layer is preferably used to smooth the surface of the semiconductor chip so that a nozzle plate may be attached to the substrate more readily. The planarization layer also functions to protect the components between the planarization layer and the surface of the substrate from corrosion.
Before holes or slots are formed in the semiconductor chip containing a planarization layer, the planarization layer is desirably masked by an etch mask layer. Like the planarization layer, the etch mask layer is typically a photoresist material. In order to complete the hole formation process, the etch mask layer must be removed. However, techniques sufficient to remove the etch mask layer may also strip away portions of the planarization layer that are needed for protection of underlying layers. This undesirable effect results in less protection for the semiconductor chip. If, on the other hand, less aggressive stripping of the etch mask layer is conducted, portions of the semiconductor chip are left with an insoluble residue from the etch mask layer which makes the chips unsuitable for use. There is, therefore, a continuing need for a process that will remove substantially all of the etch mask layer without damaging the underlying planarization and protection layer.